The present invention relates to clamps for pipes, cables, hoses and the like. More particularly, the invention relates to improvements in clamps or clips of the type wherein one end portion of a flexible band is anchored in a housing or bracket and the band has threads movable into mesh with an externally threaded rotary tightening element which is mounted in the housing.
It is already known to provide one end portion of the band which forms part of a clamp or clip with marginal recesses which receive portions of the housing to thus prevent extraction of the one end portion from the housing when the band is tightened around a pipe or the like. In many instances, the other end portion of the band and the tightening element mesh wormwise. When the tightening element is rotated in a direction to reduce the size of the loop which is formed by the band around an article or item to be clamped, the end faces of the recesses in the one end portion of the band bear against the adjacent surface of the housing with a force which increases proportionally with increasing tensional stress upon the band. In many instances, the width of the major portion of the band is less than the width of the one end portion. Therefore, such bands cannot be simply severed from a long web or strip of convoluted metallic or other material which is used for the manufacture of bands. In other words, the tool or tools for treatment of a blank of which a conventional band is made must sever the ends of the blank, provide the one end portion of the blank with the aforementioned recesses, and reduce the width of the major part of the blank. This contributes to higher cost of the band, not only because a substantial percentage of valuable material is lost due to trimming of the blank but also because the interval of time which is needed to convert a portion of a convoluted web or strip of metallic material into a finished band is relatively long. Also, the wear upon the tools which are used to sever and trim the blanks is very pronounced, especially since the material of a band which can stand pronounced stresses is hard to cut.
Another drawback of presently known clamps is that the band cannot be subjected to high or very high tensional stresses. In many instances, the laterally extending portions of the one end portion which is anchored in the housing bear against the housing with a force which is sufficiently pronounced to cause the projections to penetrate into and to cause the housing to open, i.e., they cause the housing to spread so that the one end portion of the band is extracted therefrom. The maximum permissible force which can be applied to tension the band is a function of the product of thickness of the band and of the adjacent housing wall. It was also observed that the aforementioned projections undergo pronounced deformation prior to entering the housing and causing expansion or total destruction of the housing with attendant abrupt termination of tightening action of the clamp.
It is further known to assemble a pipe clamp of a housing, a tightening screw and a band whose width is constant from end to end. That end portion of the band which is to be anchored in the housing has a centrally located rectangular slot which receives lugs projecting inwardly from the bottom wall of the housing. The extent to which the lugs project into the housing equals the thickness of the band. If the bottom wall of the housing is relatively thin, or if the band consists of a relatively thin strip stock, the retaining action of the lugs does not suffice to quarantee satisfactory retention of the slotted end portion of the band when the latter is subjected and pronounced tensional stresses. It has been observed, again and again, that the lugs are deformed or that the band breaks in the region of the slot.
In accordance with still another prior proposal, the one end portion of the band is formed with a tooth which extends from its inner side (i.e., toward the interior of the loop which is formed when the band is placed around a pipe or the like) and abuts against an end face of the bottom wall of the housing. Such connections are unreliable because the band is likely to be detached from the housing as soon as the tensional stress is relaxed. Furthermore, such connections also exhibit the drawback that the tooth is likely to be drawn into the housing in response to the application of a pronounced tensional stress upon the band.